Insects with snakes (5)
I believe the answer is:
wasps
'insects' is the definition.
(wasp is a kind of insect)
'with snakes' is the wordplay.
'with' becomes 'w' (abbreviation).
'snakes' becomes 'asps' (asp is a kind of snake).
'w'+'asps'='WASPS'
(Other definitions for wasps that I've seen before include "English Protestant stingers?" , "Striped stinging insects" , "Rugby club" , "Insects; rugby union team" , "Members of rugby team" .)